as every year I configured my computer for Christmas
Here's how it works.
At first find a Christmas-wallpaper for the background, the Google image search is useful, search only for big images.
If you have found the wallpaper, use your favorite image editing program (I use gimp) and make the wallpaper exactly fit your desktop (for example 1366x768 pixel on my laptop).
In order to use the picture as background you can select it with the configurationtools of you windowmanager or desktop environment. You can also use the xpmroot tool, but note that this tool can only handle png pictures, if you have imagemagick installed you can convert the image to png. For example if you have a wallpaper called my_santa.jpg you could use the command
convert my_santa.jpg my_santa.png
You can convert images also with gimp or any other picture-editing program. Move the image to an appropriate directory, here I use ~/.Wallpapers/
If you boot to runlevel 3 and start your windowmanager with the startx command you'll have to put the following line to your .xinitrc file (above the line where the WM is called).
Now we want snow, there's the useful program xsnow, call it in your .xinitrc (directly below the xpmroot line)
xsnow -notrees -snowflakes 250 &
don't forget the ampersand '&' at the end of the line because xsnow must run in background, otherwise your WM will likely not start properly. Read the manpage for xsnow to learn more about the options.
If you boot directly to X11 and use a displaymanager like kdm or gdm you may want to use the .xprofile file instead of your .xinitrc. If you have no .xprofile in your home directory you can create it with your favorite texteditor.
Feel free to upload a screenshot of your Christmas desktop to this thread